The present disclosure relates to the field of vertebral implants and in general to the field of implants intended to be implanted between two vertebrae to at least partially supplant an intervertebral disc. The present disclosure relates more particularly to an expansible intervertebral implant, of corpectomy cage or intersomatic cage type.
Intervertebral implants are implanted between two adjacent vertebrae to allow insertion and growth of bone tissue grafts (or substitute) in the disc space to create arthrodesis (fusion of two vertebrae). The intervertebral space, after the cage is placed, is generally filled with autologous cancellous bone or adapted bone substitutes.
Various arthrodesis techniques are known from the prior art, based on various types of implants, such as for example corpectomy cages or intersomatic cages inserted in place of a disc to promote bone growth (or arthrodesis) and secure at least two vertebrae together. Such devices are for example illustrated in French patent application FR1651637 which describes intersomatic cages for supplanting an intervertebral disc. Other examples of implants are described, for example, in the following patents or patent applications: U.S. Pat. Nos. 6,447,546, 7,291,170, 7,594,931, 8,241,359, 8,343,219, 8,409,288, 8,617,245, 9,039,774, 9,044,337, 9,173,745, US20150045893A1, US20150127107A1, US20150209089A1 and US20150320568A1.
A frequent problem in the field of vertebral implants and especially of corpectomy cages or intervertebral cages relates to the ability to maximize the stability of such implants so as to cover a volume which most closely approaches the volume occupied by the affected vertebral disc. Implants of the prior art therefore generally have substantial volume, which makes their implantation highly invasive for the patient.
A solution used for reducing the size of the implants during their implantation has been the use of expansible cages as for example described in patent application EP1699389. Such cages, once they are implanted, are deployed by the surgeon, to cover a volume approaching the volume of an intervertebral disc, while having a profile for following the lordosis of the vertebral column, thereby improving comfort for the patient and stability of the cage. Nevertheless, this type of expansible cages has a certain number of drawbacks. Indeed, during their expansion, the surgeon should exert inordinate pressure on the implant given that its expansion is simultaneously ensured on two axes orthogonal with each other. Moreover, the prior art implants are complex, deploy only in a single direction (in height, or in lordosis, or in surface area) and without stabilizing elements intrinsic to said implants. This imposes a difficulty for the surgeon in complying with a specific lordosis. In fact, this type of cage does not allow a considerable deployment amplitude and the expansion in height may therefore be insufficient for effectively restoring the height and the desired intervertebral lordosis. The expansion in surface area may be insufficient to provide support for the implant on the peripheral zones of the vertebral endplate, which is generally stronger, because the implant will remain positioned over the more central zones, causing a greater risk of collapse of the implant into the vertebral body. While generally, a distribution of the support points over a larger surface will allow better stabilization of the vertebral bodies with respect to each other.
In this context it is interesting to propose an implantable and easily expansible implant solution, which is reliable and non-invasive, adaptable in different instances of lordosis and limits risk of embrittling the adjacent vertebral structures.